Electromagnetic radiation structures have numerous applications. These applications include, but are not limited to reflecting, collecting, receiving, and/or emitting radiation within the electromagnetic spectrum (e.g., Radio Frequency (RF), Ultra-Violet (UV), visible, and Infrared (IR) radiation). The electromagnetic radiation is reflected, collected, received, and/or emitted by electromagnetic radiation structures for numerous purposes, including, but not limited to, terrestrial science, surveillance, and exploration, space science, surveillance, and exploration, and terrestrial and/or space-based communication. Electromagnetic radiation structures have continued to evolve and improve to meet past, present and future requirements to accomplish the foregoing purposes and other purposes not specifically mentioned but known to those of ordinary skilled in the art.
Generally, electromagnetic radiation structures have been configured to utilize rigid structures. For example, a rigid structure is described in U.S. Pat. Nos. 5,109,349, 4,825,062, and 4,816,759, which are hereby incorporated by reference. More specifically, the rigid structure described in U.S. Pat. Nos. 5,109,349, 4,825,062, and 4,816,759, employs mirror segments that rigid and individually controllable with three linear actuators that adjust with respect to a rigid rear surface (i.e., each of the mirror segments are tilted with respect to the rigid rear surface). Each of the mirror segments has a sensor for measuring the positioning of the mirror segment with respect to the rigid rear surface (i.e., measuring the tilt of the mirror segment with respect to the rigid rear surface), and each of the mirror segments is individually controllable using tilt error data obtained from a sensor of each mirror segment and sensors of neighboring mirror segments. While this structure provides an accurate surface figure, there are attributes and characteristics introduced by the rigidity that are less than desirable and limiting.
For example, the rigid structure described in U.S. Pat. Nos. 5,109,349, 4,825,062, and 4,816,759, requires the rigid rear surface for positioning of the mirror segments. Therefore, this configuration is generally not applicable to flexible materials (e.g., light weight truss beams, membranes or films that are inherently non-rigid) that can be used to form electromagnetic radiation structures. In addition, tilt control of each mirror segment using tilt error data for a mirror segment and tilt error data for neighboring mirror segments as described in the foregoing patents assumes that the surface of the electromagnetic radiation structure is divided into separate and distinct segments, which are separately controllable and generally isolated from other segments. However, as flexible materials are generally unitary without distinct segments, positioning or movement of one portion of the flexible and lightweight film is likely to cause surface deformation that propagates to other portions of the material, and the prior art methods and apparatus for controlling the surface figure of the material are generally inadequate and will not provide the desirable accuracy.
In view of the foregoing, it should be appreciated that it would be desirable to provide an electromagnetic radiation structure that uses a deformable truss beam or a flexible membrane and also provide methods and apparatus for measuring the surface figure of a flexible material to provide a desired surface figure for electromagnetic radiation. Furthermore, additional desirable features will become apparent to one of ordinary skill in the art from the foregoing background of the invention and following summary and detailed description.